On a recent United flight, my husband and I upgraded from coach to first class. They assured us there would be no change fee. The very next day our Amex was hit with a $400 fee from United. Thinking this would be an easy fix, we called United. A very rude man in India, assured us that yes this was a mistake but the only way to get our money back was to complete a very lengthy on line form. My husband completed the form only to have the form black out when we went to send it to United. Think about it, what an amazingly clever scam, they took our money, admit it was their mistake and now they are sitting on it while we try to jump through hoops to get it back! If it weren't such a large sum, we might be tempted to say screw it and walk away. Bet that's what they're hoping!